The present invention relates to a general purpose circuit interrupting device using neutral line tripping with and without ground fault interruption.
Within the commercial, industrial and residential communities there exists a need for an inexpensive circuit interrupter capable of detection of a potentially undesirable event, which may cause harm to people or property, and permanently interrupt power from the interrupter to the load. An undesirable event would include, a shock or vibration such as from an earthquake, temperature, pressure, or humidity condition, or any other measurable phenomenon.
If the conventional circuit breaker is employed as a means of accomplishing this result, and especially if the breaker is located remotely to disconnect the line voltage, there is the consideration that across the circuit breaker is the line voltage which may be undesirable to bring into the location where the phenomenon is to be detected.
In contrast to circuit breakers which open a circuit in response to excessive current flow which may be caused, for example, by a short circuit in a load, a ground fault interrupter (GFI) acts to prevent electrical shocks by detecting unbalanced current flow between the hot and neutral lines of a circuit. The presence of the unbalanced current flow signals that there is leakage somewhere to ground which is dangerous to a person who may come in contact with the leakage current which is present between the GFI and the load. A circuit breaker is not sensitive to such a condition and therefore will not act to protect a person exposed to the line voltage.
Hence, neither the circuit breaker nor the ground fault interrupter is suitable for use to disconnect line voltage upon the occurrence of a specific event of the type mentioned earlier.
Elaborate schemes, however, can be devised to provide low voltage switches with a separate power supply to actuate the circuit breaker from a remote location, but such arrangements are uneconomic, and may be unfeasible due to the expense involved or the complicated nature of such an arrangement.
A number of U.S. patents show devices which act to disconnect line voltage from a load under certain conditions. U.S. Pat. No. 4,282,500 discloses a ground fault interrupting device which includes a test circuit. U.S. Pat. No. 4,288,768 shows a circuit breaker which responds to both short circuit current and earth leakage. U.S. Pat. No. 4,568,997 describes a ground fault interrupter device with a latching solenoid. U.S. Pat. No. 4,630,015 discloses a ground fault circuit interrupter which utilizes cam actuators as part of the solenoid. U.S. Pat. No. 4,641,217 shows a two pole ground fault circuit breaker incorporated into a single assembly. U.S. Pat. No. 4,686,600 describes a modular ground fault circuit breaker providing ground fault, short circuit, and overcurrent circuit protection. The article entitled "Simplify Design of Ground Fault Interrupter" by Stolitzka et al appearing in "Electronic Design", pp 61-65, May 25, 1989 describes current designs for GFI's. None of the preceding patents or the referenced document teaches the present invention.